1. Field of the Invention
This invention relates to instrumentation systems for use by scuba divers. More specifically, the present invention relates to a display system that displays pertinent dive data directly in the diver's line of sight without substantially obstructing his vision. Furthermore, it relates to a diver's instrumentation system that allows a diver to set his dive parameters before a dive, that monitors these parameters during a dive, and provides warnings when exceeded. Sensors are provided that detect air tank pressure, depth and water temperature. Storage of pertinent dive data including warnings is provided for downloading into an external computer.
2. Prior Art
Since the advent of scuba equipment, divers have been able to remain under water for extended periods of time. (Scuba is a acronym for "Self Contained Underwater Breathing Apparatus"). On a typical dive, a scuba diver may remain underwater for a period of time that often extends from a half hour to one hour. The amount of time spent underwater depends principally upon the rate at which air is used by the diver during his dive which in turn is determined by a number of factors such as the depth of dive, the length of the dive, the diver's physical condition and weight, and the amount of activity exerted in the dive. Other factors that may affect the amount of time spent underwater include subjective factors such as the degree to which the diver is enjoying the dive and completion of the task at hand. Safety, a primary concern, is still another factor affecting the length of time that a diver remains underwater.
Scuba equipment typically includes one or more cylindrical tanks for storing compressed air, an air valve attached to the air tank and a regulator connected to the valve. A typical regulator comprises a apparatus which allows the diver to draw air from the tank as he inhales. While exhaling, the expelled air escapes through passages provided in the regulator.
Regardless of the type of regulator or other breathing apparatus, dive safety is a primary concern, whether the diver be recreational, commercial or even a military diver. Safety plays such an important concern in scuba diving that all dive shops require proof of completion of an accredited diving program as a condition for purchasing compressed air (i.e., having compressed air tanks refilled in preparation for a dive).
One of the most obviously dangerous conditions confronting a scuba diver is the possibility of drowning in the underwater environment. This is a realistic possibility if, while underwater, the diver were to expend all of the air in his air tank. The diver may not be aware of his predicament until he attempts to inhale from the tank and receives nothing. In that suddenly dangerous situation, the diver's alternatives are to either find another source of compressed air (such as from a buddy) or to attempt to surface as quickly as possible. Neither of these alternatives is assured; a buddy may not be close enough to be of assistance, or the surface may be too distant to safely make the ascent. Also, the "quick surfacing" option creates additional dangers which will be described in the following paragraph. The best solution requires the diver to constantly monitor the air available in his tank and to surface with a substantial safety margin of air remaining.
In addition to the danger of drowning, other dangers are associated with breathing compressed air under water. These dangers are familiar to anyone who has completed a diving program and include decompression sickness (the "bends") and air embolism. Decompression sickness results when the diver has been breathing compressed air underwater for an extended period of time. The length of time breathing compressed air that will create a "bends" problem depends upon the depth of the dive and the number of dives that the diver has completed that day. During such an extended period of time breathing compressed air, the blood absorbs a substantial percentage of nitrogen. When the diver ascends, the pressure surrounding his body decreases and if enough nitrogen has built up in his blood, bubbles will form therein, leading to life-threatening decompression sickness. Prevention of decompression sickness is the common solution to this problem. The U.S. Navy has developed decompression tables which, if followed by the diver, allow a substantially safe dive. When using these tables, it is critical to know the maximum bottom time for a given depth, which is defined by the total time a person is underwater for a specific maximum depth of dive. For this purpose, it is often critical to know the maximum depth of the dive and its total elapsed time.
The second problem above-mentioned is that of the air embolism. An air embolism occurs when a diver is ascending while holding his breath. In that case, the air expands in the diver's lungs, causing them to rupture. An air embolism presents a life-threatening situation which has resulted in death. To prevent an air embolism, the diver must always exhale while ascending in order to relieve the excess pressure building up in his lung. Additionally, a cautious diver ascends slowly enough to help minimize the possibility of such an occurrence.
Common safety instrumentation includes an air tank pressure gauge and a depth gauge. Typically these devices have been mechanical, however in recent years, a number of devices including electronic instrumentation have been available. For example, Oceanic.RTM. produces the Data Master, a pressure activated digital data console that can monitor tank pressure, depth, maximum depth, surface interval and count the number of dives. The digital data is displayed on a liquid crystal display housed in a waterproof shell that is connected to the air tank. This product also allows display of other information, such as dive time remaining, "no decompression" information, and a flashing warning indicator that appears ten minutes before a "no decompression" limit to ten minutes after exceeding the limit. Furthermore, a pre-dive planning feature can scroll through programmed depths and displays maximum allowable bottom time based upon previous dive profiles. Also, a temperature display is provided. Other digital gauges, such as the JM Cousteau digital gauges offer digital readouts of diving functions such as tank pressure, current and maximum depth readings, and bottom time.
Neither of these devices is easily viewable. Each system includes a LCD display mounted on a separate module, which is attached to other equipment such as the air tank and buoyancy compensator. To view the data appearing on the LCD display, the diver must make a specific and concentrated effort to find this module. Furthermore, the cumbersome equipment worn by a diver can substantially impede his efforts to locate the display module. Also, a diver commonly becomes preoccupied with the underwater scenery or his current task, and he may simply forget to constantly review the important safety data provided on the display.
To continually apprise the diver of his situation, it has been suggested that mechanical gauges be affixed to the diver's mask outside of his line of sight, in a position opposite two reflecting surfaces affixed to the face mask. The gauges and the reflecting surfaces are all physically located in the water outside of the diver's mask. The two reflecting surfaces are located offset from the usual line of sight, but encompassed by the diver's field of vision. There is also an optical path from the gauges to the reflecting surfaces so that the diver can see the gauges from their reflection. This is a cumbersome and unwieldy arrangement.